1. Field of the Invention
The present invention relates to a process for producing noodles which process improves qualities thereof such as a feeling upon eating, by using (1) a transglutaminase, (2) a carbonate and/or a reducing agent and, optionally, a protein partial hydrolyzate, together with a starting cereal flour, in the production of noodles, and an enzyme preparation containing (1) a transglutaminase, (2) a carbonate and/or a reducing agent and, optionally, a protein partial hydrolyzate as the active ingredient, the enzyme preparation being to improve qualities of noodles and other protein-containing foods.
As the noodles targeted by the present invention, there may be mentioned Japanese noodles such as Japanese udon made from wheat flour as the main starting material, Japanese soba (buckwheat noodle) made from buckwheat flour as the main starting material, and the like, Chinese noodles (including sheets of wonton, shao-mai or siew mai and Japanese gyoza or filled dim sum) obtained by using an alkali agent such as Japanese kansui (a mixture of alkaline salts) or the like, together with wheat flour as the main starting material, pasta made from durum semolina flour, such as spaghetti and the like, and so forth.
2. Background Prior Art
As is well known, there are among noodles, Chinese noodles, Japanese noodles such as soba, udon and the like, pasta (western noodles), and so forth. With respect to these noodles, products produced by various treatments such as boiling, drying, semi-drying, steaming, frying and the like, of raw noodles for improving the instant property or instantaneousness in serving at table thereof, have been put on the market.
These products are expected to provide glutinousness and elasticity simultaneously, namely, viscoelasticity (Japanese koshi, or firmness or chewiness) when eaten, and having a good texture which is provided by raw noodles immediately after boiled. Especially, instant noodles obtained by frying are further expected to have such a quick restoration in hot water that they can be eaten in a short period of time. However, when such instant noodles get quickly restored in hot water, they tend to be less firm. Further, when they are stored for a long period of time, it gives rise to such problems that their appearance is impaired owing to a phenomenon such as browning or the like, and so forth.
Accordingly, these instant noodles are required to have such a good texture that with respect to the feeling upon eating of noodles when restored in hot water, the glutinousness and the elasticity are provided over a long period of time and especially the glutinousness is maintained. Various improvements therefore have been proposed. For example, there is disclosed in JP-B-9-2642859, a method where pregelatinization of starch is conducted using trehalose, followed by drying and then frying treatment and the like. Further, there is disclosed in JP-B-6-9475 another method where raw noodles are boiled, and then steamed with superheated steam to secure a good texture after restoration. Still further, there is disclosed in JP-A-9-86572 a method slit lines by which to form holes for draining hot water are applied to improve restoration in hot water. Furthermore, there is disclosed in JP-B-7-32681 a method where a firm and elastic texture is provided by using a combination of corn starch, green gram starch and alum. Moreover, there is disclosed in JP-B-7-32682 a method where instant noodles are produced by boiling treatment and hot-air drying treatment. There is disclosed in JP-A-6-225744, an instant property or instantaneousness and a shape retention are obtained by incorporating a water-soluble protein powder and a water-swellable protein powder into the raw food material. There is disclosed in JP-A-5-176698 a method where instantaneousness and restorability are provided with a mixing ratio of starting wheat flour and starch.
However, in accordance with the above-described methods where the treatments with the different mixing ratios of the starting flour and other starting materials, and the different conditions of heating, boiling and the like are employed, the resulting noodles are not said to be satisfactory instant noodles having improved noodle qualities. Nor have been the problems such as browning and the like solved. For these reasons, further improvements have been in demand. In other words, it is required to provide to instant noodles a texture closer to that of raw noodles immediately after boiled by improving an elasticity and a glutinousness, i.e., a texture peculiar to instant noodles.
Under the above-mentioned background of the prior art, it is an object of the present invention to provide noodles of which the texture is improved by imparting a good balance between elasticity and glutinousness to ordinary noodles of which functions such as convenience, restorability, shelf stability and the like are required.
The present inventors have assiduously conducted investigations to achieve the above-mentioned and other objects, and have consequently found that noodles having a firmness with a good balance between glutinousness and elasticity inherent in noodles upon eating, can be produced by conducting an enzyme reaction that improves noodles in their qualities using the enzymatic activity of transglutaminase, in the presence of a carbonate and/or a reducing agent and, optionally, a protein partial hydrolyzate, further that it is possible thereby to prevent the softening of noodle strands in the drying and to improve glutinousness, and still further that it is, in turn, possible to produce various noodles having an excellent texture closer to that provided by raw noodles immediately after boiled. These findings have led to the completion of the present invention.
Accordingly, the present invention relates to an enzyme preparation for noodles and other protein-containing foods, characterized by containing, as the active ingredients, (1) a transglutaminase and (2) a carbonate and/or a reducing agent and further, optionally, a protein partial hydrolyzate, and to a process for producing noodles characterized in that in addition to starting materials such as cereal flour as the main starting material and the like, (1) a transglutaminase and (2) a carbonate and/or a reducing agent and further, optionally, a protein partial hydrolyzate are used.
The invention will be successively described in detail below.
First of all, a process for preparing the enzyme preparation of the present invention which can effectively be used in producing noodles and other protein-containing foods, namely, a process for preparing an enzyme preparation characterized by containing, as the active ingredients, (1) a transglutaminase and (2) a carbonate and/or a reducing agent and, optionally, a protein partial hydrolyzate and/or further a pH modifier, will be described first, on the assumption that it is used mainly in the production of noodles.
The transglutaminase is, as is well known, an enzyme that catalyzes the acyl transfer reaction of a xcex3-carboxyamide group of a glutamine residue in the peptide chain of protein such as wheat gluten. This transglutaminase acts on an xcex5-amino group of a lysine residue in protein as an acyl receptor to form an xcex5-(xcex3-Glu)Lys crosslink intermolecularly between the protein molecules or intramolecularly in the protein molecule, whereby the network structure of wheat gluten is further enhanced.
This transglutaminase includes a calcium-independent one and a calcium-dependent one. Either can be used according to the present invention. As the former one, those derived from microorganisms such as Actinomycetes, Oomycetes, Bacillus subtilis or the like can be mentioned (refer to, for example, J-A-64-27471). As the latter one, there may be mentioned those derived from guinea pig liver (refer to, for example, JP-B-1-50382), those derived from animals such as bovine blood, swine blood and the like, those derived from fishes such as salmon, red sea bream and the like (refer to, for example, Seki Nobuo et al., xe2x80x9cNippon Suisan Gakkaishixe2x80x9d, vol. 56, No. 1, pp. 125-132 (1990)), those derived from oyster, or so forth. On top of that, those produced through gene recombination (JP-A-1-300889, JP-A-6-225775, JP-A-7-23737 and the like) can be mentioned. In accordance with the present invention, any of these transglutaminases can be used, and the origin and the process for producing the same are not particularly limited. However, in view of the function and the economics in the food applications, the calcium-independent transglutaminases are preferable. For example, the transglutaminases derived from the microorganisms (JP-A-64-27471 mentioned above) meet any conditions, and are said to be optimal at present.
By the way, the activity unit of the transglutaminase referred to concerning the present invention is measured and defined as follows. That is, the reaction is conducted using benzyloxycarbonyl-L-glutaminylglycine and hydroxylamine as substrates. The resulting hydroxamic acid is formed into an iron complex in the presence of trichloroacetic acid, and an absorbance at 525 nm is then measured. A calibration curve is established from the amount of hydroxamic acid, and the amount of the enzyme in which to form 1 xcexcml of hydroxamate for 1 minute is defined as 1 unit, an activity unit of the transglutaminase (refer to JP-A-64-27471 also).
Next, the carbonate which can be used to prepare the enzyme preparation of the present invention will be described.
According to the present invention, the carbonate allows occurrence of carbon dioxide gas through heat treatment in a noodle dough to give the noodle dough a porous structure through the bubbling action within the noodle dough. Further, in the course of further strengthening the network structure of wheat gluten by the action of the transglutaminase crosslinking polymerization, the carbonate is heated to generate carbon dioxide gas, whereby the noodle dough is swollen and the noodle material rapidly absorbs water in, for example, the restoration in hot water.
Examples of the carbonate having such a function include carbonates of alkali metals such as sodium, potassium and the like, carbonates of alkaline earth metals such as calcium, magnesium and the like, hydrogencarbonates of alkali metals such as sodium, potassium and the like, and hydrogencarbonates ofalkaline earthmetals such as calcium, magnesium and the like. Some of these carbonates are, as is well known, ordinarily used as kansui (mixture of alkaline salts) to increase Japanese koshi or firmness of Chinese noodles in the production thereof. Specific examples thereof include sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate and the like. The carbonate to be incorporated in the enzyme preparation of the present invention is not particularly limited. Sodium carbonate, sodium hydrogencarbonate and the like are preferable. In view of heat stability and the like, sodium hydrogencarbonate is preferable.
As the reducing agent, there can be mentioned reducing sugars such as maltose, lactose, glucose and the like, thiol compounds such as glutathione, cysteine and the like, and so forth. In view of the taste, it is especially preferable to use glutathione.
As glutathione, commercial glutathione may be used, and yeast extract containing glutathione in a large amount or the like can also be used.
By the way, according to the present invention, the reducing agent acts on the xe2x80x94Sxe2x80x94Sxe2x80x94 bond of wheat gluten to increase the glutinousness of noodles or the like and impart a desirable texture to noodles.
Further, as the protein partial hydrolyzate, a partial hydrolyzate made from wheat protein, milk protein, soybean protein or the like as a starting material is useful. The partial hydrolyzates of these proteins are not particularly limited so long as the object of the present invention is achieved. Incidentally, according to the present invention, the protein partial hydrolyzate has such effect that it acts on the network structure of the wheat protein to give the noodles a flexible elasticity.
A partial hydrolyzate of wheat protein may be obtained by, for example, partially hydrolyzing wheat protein with an enzyme, an acid, an alkali or the like. Although it is not particularly limited, a wheat protein partial hydrolyzate product having a deamidation rate of from 2 to 85% can be used. The rate of deamidation is generally an index that indicates a degree of formation of xcex1-amino acids which are formed when a protein is hydrolyzed by the catalytic activity of an enzyme, an acid or an alkali. Incidentally, commercial xe2x80x9cGlutamine Peptide Compositionxe2x80x9d (for example, xe2x80x9cGlutamine Peptide Compositionxe2x80x9d supplied by K. K. Canpina Milk Uny Japan) is also a wheat protein partial hydrolyzate, and it is therefore included in what is meant by the wheat protein partial hydrolyzate according to the present invention.
The partial hydrolyzate of a milk protein will be next described. The milk protein here refers to casein, its salt, a whole milk powder, a skim milk powder or the like. Any of these can be used as the starting material, to obtain a milk protein partial hydrolyzate. However, salts such as sodium caseinate and the like are generally appropriate in view of workability and the like. As the milk protein partial hydrolyzate to be used according to the present invention, like the wheat protein partial hydrolyzate, a product obtainable by hydrolyzing a milk protein with an enzyme, an acid, an alkali or the like can be used. Although it is not particularly limited, a milk protein partial hydrolyzate product having a deamidation rate of from 5 to 75% can ordinarily be used.
Next, a partial hydrolyzate of the soybean protein will be described. The soybean protein here refers to a soybean protein isolate extracted from soybeans, a soybean protein concentrate, a soybean powder obtained by pulverizing whole soybeans as such, soybean grits and the like. These are partially hydrolyzed with an enzyme, an acid, an alkali or the like to obtain a soybean protein partial hydrolyzate. A soybean protein partial hydrolyzate product having a rate of hydrolysis (rate of deamidation) of from 5 to 75% can ordinarily be used. However, it is not particularly limited unless the object of the present invention is impaired. A product having a rate of hydrolysis of from 20 to 70% is preferable.
It is not particularly difficult to prepare the enzyme preparation of the present invention containing a transglutaminase and a carbonate and/or a reducing agent and, optionally, a protein partial hydrolyzate as the active ingredients, as described above. The preparation can properly be conducted according to the conventional process known in this field except that a transglutaminase and a carbonate and/or a reducing agent as the essential active ingredients and a protein partial hydrolyzate as the optional ingredient are incorporated.
In the enzyme preparation of the present invention can of course be incorporated food filler(s) such as starch, dextrin, lactose and the like for the reasons of preparations or in view of the convenience in use. Further, a modifier such as starch, modified starch, albumen (egg white), wheat gluten or the like, a thichening polysaccharide, an acidulant and the like that are auxiliary starting materials ordinarily used in the production of noodles, can be used in the enzyme preparation of the present invention, and these are not particularly limited so long as the object of the present invention is achieved. Further, it may contain an enzyme stabilizer (such as calcium chloride, ascorbic acid or the like) or an auxiliary starting material to improve powder characteristics (solubility, dispersibility, prevention of powder scattering and the like) of the enzyme preparation.
Needless to say, it is preferable that the ratio at which to mix a transglutaminase with a carbonate and a reducing agent or a protein partial hydrolyzate which are to be incorporated into the enzyme preparation of the present invention is, for example, a ratio at which to satisfy, at the same time, necessary amounts of the transglutaminase, the carbonate, the reducing agent and the protein partial hydrolyzate in the process for producing noodles according to the present invention as will be later described. Such a mixing ratio is of such that per one unit of the transglutaminase, the carbonate is between 0.0001 to 30 g, the reducing agent is between 0.00001 and 1 g and the protein partial hydrolyzate is between 0.00001 and 10 g.
The enzyme preparation of the present invention can further contain a pH adjusting agent in view of the color and the physical properties of noodles.
The pH adjusting agent is a phosphate used in ordinary noodles or the like. For example, sodium hydrogenphosphate can be mentioned. However, it is not particularly limited thereto unless the object of the present invention is impaired.
Now, the enzyme preparation of the present invention naturally imparts glutinousness and elasticity to noodles, as is clear from the above-described functions of the respective ingredients. Further, it is generally useful for protein-containing foods made from cereals such as wheat flour and the like as the main starting material. For example, it imparts a preferable texture to, for example, various noodles, confectionery such as biscuits, cake mixes, cakes and the like, various types of bread, and the like which are foods containing wheat protein, by the crosslinking polymerization of the protein, and it causes the same to exhibit effective functions.
Thus, the enzyme preparation of the present invention has been described mainly with respect to noodles made from cereals such as wheat flour and the like as the main starting material. It goes, however, without saying that the same effect of improving the texture can be given to foods containing proteins which can be substrates of the transglutaminase.
Second, the process for producing noodles of the present invention will be described.
The noodles to be produced by the process of the present invention widely include Chinese noodles (including sheets of Japanese gyoza (filled dim sum), spring roll and wonton), Japanese noodles such as Japanese udon, Japanese soba and the like, pasta (western noodles) such as spaghetti, macaroni and the like, and so forth. Further, raw noodles, boiled noodles, dried noodles, semi-dried noodles, steamed noodles or fried noodles (packed in a cup or the like) and the like which are distribution style different in the degree of instant processing, are widely included therein.
It is not particularly difficult to produce such various types of noodles by the process of the present invention using, in addition to the starting materials such as cereal flour as the main starting material, (1) a transglutaminase and (2) a carbonate and/or a reducing agent and, optionally, a protein partial hydrolyzate. This is because the noodles can be produced according to the conventional process for producing noodles including the types of the starting materials, the mixing ratio and the like, except, in addition to the ordinary starting materials, a transglutaminase and a carbonate and/or a reducing agent and, optionally, a protein partial hydrolyzate are used in the step of forming the noodle dough. Of course, the transglutaminase and the carbonate and/or the reducing agent and, optionally, the protein partial hydrolyzate can also be used in the form of the enzyme preparation (naturally, including a product containing a food filler) of the present invention as described above.
Incidentally, such a process for producing noodles will be outlined, as follows. Noodle dough is formed using various auxiliary starting materials, together with the main starting material cereal flour such as wheat flour, buckwheat flour or the like; the resulting dough is aged (rested), combined, and rolled to obtain a dough sheet (cut to a desired shape at this stage in case of sheets of gyoza, spring roll and wonton); and the resulting sheet dough is further cut to noodle strands. The resulting noodle strands are put in commercial distribution, (a) directly as raw noodles, (b) as dried noodles or semi-dried noodles by being dried, (c) as boiled noodles by being boiled, or (d) as fried noodles by being fried.
Then, the manners how the transglutaminase, the carbonate, the reducing agent and the protein partial hydrolyzate are used, will be mainly described below.
The amount of the transglutaminase to be added (or used), is between 0.01 and 30 units, preferably between 0.1 and 10 units per one gram of the protein present in the starting cereal flour. If the amount added is less than the above-mentioned range, the expected effects cannot be provided with respect to the improvement of the texture of noodles, the physical properties after drying treatment and steaming treatment, prevention of softening of noodles on standing after boiling and the like. If it exceeds the above-mentioned range, the texture of noodles gets notably too hard inconveniently. Thus, neither case can satisfactorily achieve the object of the present invention.
The amount of the carbonate to be added is between 0.0001 and 30 g, preferably between 0.001 and 3 g per one unit of the transglutaminase. If the amount added is less than the above-mentioned range, no effect by the combination with the transglutaminase is observed. While, if it exceeds the above-mentioned range, the texture based on the peculiar hardness provided by the carbonate is gives undesirably. Thus, neither case can satisfactorily achieve the object of the present invention.
Further, the amount of the reducing agent to be added is between 0.001 and 2.0% by weight based on the cereal flour as the main starting material. If the amount added is less than the above-mentioned range, glutinousness is exhibited to a lower extent. If it exceeds the above-mentioned range, glutinousness is increased too much. Thus, neither case can satisfactorily achieve the object of the present invention.
The amount of the protein partial hydrolyzate to be added is between 0.00001 and 10 g, preferably between 0.0001 and 1 g per one unit of the transglutaminase. If the amount added is less than the above-mentioned range, the texture of noodles is the same as that given by the transglutaminase alone, and no additional effect by the combined use is observed. Whereas, if it exceeds the above-mentioned range, a texture with the decreased elasticity peculiar to the protein partial hydrolyzate is provided undesirably. Thus, neither case can satisfactorily achieve the object of the present invention.
Further, a modifier such as starch, modified starch, albumen, wheat gluten or the like, a thickening polysaccharide, acidulant, a pH adjusting agent and the like which are auxiliary starting materials used in the production of noodles as has been mentioned earlier, can be used, and they are not particularly limited so long as the object of the present invention is achieved.
Incidentally, in order to exhibit the enzymatic activity, a mixture of the enzyme and the substrate has to be generally maintained under conditions of temperature, time and the like that are suitable for the enzymatic activity to be exhibited. However, in the production of noodles according to the present invention, the enzymatic activity of the transglutaminase is sometimes exhibited, for example, during the ageing of the noodle dough without special consideration of such conditions. Further, the step of ageing the noodle dough can be conducted under such conditions as required, whereby the enzymatic activity of the transglutaminase is exhibited. Further, the dough sheet obtained by combining and rolling a noodle dough is maintained under such conditions, whereby the enzymatic activity of the transglutaminase can also be exhibited.
Further, in order that carbon dioxide gas may be generated from the carbonate and by the bubbling action thereof, the noodle structure may be made porous (swollen), noodle strands can be cut out from the dough sheet, then steamed and subjected to heat treatment such as frying or the like.
The process for producing noodles of the present invention is, as stated above, a process for producing noodles characterized by using, in addition to the starting materials such as cereal flour and the like as the main starting material, (1) a transglutaminase and (2) a carbonate and/or a reducing agent and optionally, a protein partial hydrolyzate. The following can be mentioned as embodiments of the process for producing noodles of the present invention, in consideration of such points as described carlier on the activities of the transglutaminase and the carbonate.
(a) The sheet dough is subjected to ageing treatment at a temperature of from 0 to 60xc2x0 C. for 15 minutes or more.
(b) The noodle strands (raw noodles) cut out from the sheet dough are directly handled as a product. In this case, these are put in commercial distribution as raw noodles.
(c) The raw noodles are boiled to provide a product. In this case, the boiled noodles or frozen noodles obtained by freezing the same are put in commercial distribution.
(d) The raw noodles are (semi-)dried to provide a product. In this case, they are put in commercial distribution as (semi-)dried noodles.
(e) The raw noodles are heated with the use of steam to gelatinize the starch on the surfaces alone, providing a product. The resulting noodles are so-called steamed noodles.
(f) The raw noodles are steamed to gelatinize the starch, and then dried to provide a product. The resulting noodles are so-called non-fried instant noodles.
(g) The raw noodles are steamed to gelatinize the starch, and then fried to provide a product. The resulting noodles are so-called instant noodles.
(h) The raw noodles are fried as such to provide a product.
(i) The raw noodles are twice fried, first as such at a low temperature and then at a high temperature to provide a product. The resulting noodles are so-called snack noodles. The snack noodles refer to noodles that have been fried and are eaten in this state.
(j) The raw noodles are steamed, and then followed by twice frying as referred to under (i) above, to provide a product.
(k) The raw noodles are treated with an acid, and then followed by heating, to provide a product.
Further to the foregoing, in order to sufficiently exhibit the activity of the transglutaminase, the noodle strands are cut out from the noodle dough obtained by kneading or mixing the starting materials, and these (raw) noodle strands are then subjected to such two-step frying that these are first fried, e.g., at from 15 to 80xc2x0 C., preferably from 35 to 55xc2x0 C. for from 30 to 240 seconds, and then at from 105 to 190xc2x0 C., preferably from 130 to 160xc2x0 C. for from 90 to 150 seconds (refer to the above-mentioned (i)). Alternatively, the noodle dough is previously combined and rolled, and the resulting dough sheet is then subjected to such ageing treatment that it is maintained at a temperature of at least 0xc2x0 C. and at most 65xc2x0 C. for from 15 minutes to a night, for example. Then, the activity of the transglutaminase is exhibited sufficiently (refer to the above-mentioned (a)). Thereafter, the two-step frying is conducted under the above-mentioned conditions. Further, after the noodle strands are cut out, these are directly (as raw noodles) subjected to the drying step immediately (refer to the above-mentioned (d)) Or, after being steamed, these are, for example, fried first at a low temperature of from 50 to 60xc2x0 C., and then at a high temperature of from 70 to 190xc2x0 C. (refer to the above-mentioned (j)). As a result, the water content is reduced, so that the noodles can also be put in commercial distribution in the form of (semi-)dried noodles by being semi-dried or dried. In this manner, according to the present invention, the various types of noodles can be produced as those having a good texture with an elasticity and a glutinousness regardless of the form of the product.